Interest in contraceptive devices fixed to the wall of
uterus appeared first of all in the field of positioning I.U.D.s during the period immediately subsequent to confinement or post-partum period. Intrauterine contraception is in fact considered by the experts as an effective, cheap and temporary means of contraception, temporary being meant in the sense that, once the intra-uterine device is withdrawn, pregnancies are again possible. Moreover, the post-partum period is considered to be a strategically important period for the insertion of an intra-uterine device, this being particularly true in countries where women have relatively little contact with medical services. In effect, at the time of confinement, the motivation to use contraceptive devices is great; moreover, at that moment the insertion of a contraceptive device is easy, painless, does not cause additional bleeding and can be untertaken by the nurse or midwife. Another advantage, if insertion of the intra-uterine device is undertaken immediately after confinement, is that the patient remains under medical supervision for at least several hours after insertion. Furthermore, positioning of an intra-uterine device does not interfere with breastfeeding, and nor does it require the intervention of medical personnel other than those already involved in the confinement
However, immediately after confinement, the dimensions of the uterine cavity and the neck of the womb are large, a fact which entails significant risks of rejection and/or displacement of the intra-uterine device.
This is one of the reasons which have led to the designing of intra-uterine devices fixed to the wall of the uterus. Such devices have been described in particular in US-A-3 954 103 and BE-A-899 286.
Another reason for fixing the intra-uterine device to the wall of the uterus is that this method permits the use of highly deformable intra-uterine devices which, without this fixing, would be expelled from the uterus. In fact, a highly deformable intra-uterine device is better tolerated in the uterus, and runs less risk of causing damage to the wall of the uterus, than a device held in the uterus by its shape. Such devices have been described in particular in EU-A-0100924 and BE-A-901 652.
Various retaining members, implantable in the wall of the uterus, have been described in these prior documents.
As stated above, an intra-uterine contraceptive device has the advantage of being a temporary device, that is to say, capable of being removed. If it is wished to keep this advantage when contraceptive devices are used which are fixed to the wall of the uterus, it is thus also necessary to be able to release the fixture from the wall of the uterus. If, at the time of insertion and fixing of the intra-uterine device to the wall of the uterus, use is necessarily made of a device for introducing and fixing the contraceptive device, it would seem impossible to have to use a device to release the fixture, which can as a rule only be effected by drawing and pulling. Insofar as this is the case, it would seem difficult to remove the retaining member implantable in the tissue of the uterus described in EU-A-0100924 from the tissue of the uterus without causing considerable damage thereto. The same is true of the pulling-out of the point shown in US-A-3954103 and nevertheless advocated in this Patent.
This is the reason why, in its prior Patents BE-A-899 286 and BE-A-901 652, the Applicant principally envisages, as the retaining member implantable in the tissue of the uterus, a small deformation of the thread, especially such as a knot formed in the thread.
In effect, such an implantable retaining member has the advantage, first of all, of achieving suitable fixing to the tissue of the uterus, at least outside the post-partum period, and, moreover, of enabling releasing of the fixture, by pulling, without damaging the wall of the uterus.
However, experience has shown that a small deformation of a form suitable for preventing damage to the wall of the uterus at the time of withdrawal, such as knot in the thread, may be insufficient to ensure satisfactory anchorage in the tissue of a uterus during the immediate post-partum period The tissue of a dilated uterus, immediately after confinement, is, in fact, much less firm than the tissue of a uterus in the normal state.